农林科学最新文献

This study examined the genetic diversity in a collection of field isolates of Ornithobacterium rhinotracheale and compared that with the diversity in the serovars A-D and F-I reference strains and available whole genome sequences. Phylogenetic analysis of the 16S rRNA gene of the nine Australian isolates and twelve sequences of overseas isolates resulted in six clusters with the Australian isolates not closely related to either the type strain or the serovar reference strains. The suitability of low-cost finger printing techniques, ERIC-PCR and rep-PCR, when applied to O. rhinotracheale were also evaluated. The fingerprints generated through ERIC-PCR were more informative and this method subsequently used to examine the genetic diversity of the isolates and the reference strains. The ERIC-PCR patterns confirmed the isolates and strains were quite diverse, with 15 different patterns detected. These results suggested that the Australian isolates were genetically distinct from the overseas strains, consistent with the genetic distinction observed in the phylogenetic study. Whole genome sequences of the Australian isolate BR2963 and the 15 genomes identified as O. rhinotracheale in the Genome Taxonomy Database confirmed that serovars F, K and M form a cluster distinct from other O. rhinotracheale and probably represent a distinct species within the genus Ornithobacterium. Additionally, the Australian isolate BR2963 had an average nucleotide identity level with the O. rhinotracheale type strain (DSM15997^T) below the accepted 95% threshold for species suggesting that the isolate is a member of the genus Ornithobacterium but not within the species rhinotracheale.

Seven lines of major histocompatibility complex (MHC)-B congenic specific pathogen free (SPF) chickens and two lines of non-B congenic SPF chickens with similar B haplotype but differing non-MHC genes were utilized to investigate the effect of the B locus on infectious bursal disease (IBD) development. In initial experiments, chickens were challenged at 28 days of age with the variant infectious bursal disease virus (IBDV) strain AL-2, classical IBDV strain STC, or very virulent (vv) IBDV strain rA. IBD severity was evaluated throughout the 7-day course of infection by assessing survivability and histopathological analysis of bursal lesion scores. Follow-up studies investigated the effects of varying STC challenge doses on IBD development. Results demonstrated that the challenge strain of IBDV has a large impact on B locus-based genetic resistance. The most significant differences in survivability and bursal lesions were noted after challenge with the vvIBDV strain, with MHC-B congenic chicken lines B*13 and B*19 being the most susceptible. Based on survivability, the B*19 chicken line was also characterized as the most susceptible after challenge with high doses (10⁵ EID₅₀) of the STC strain. No differences in survivability were detected among the chicken lines when challenged with the variant strain AL-2. Based on the results with these chicken lines, B locus-based genetic resistance to IBDV is mainly associated with survival during the early stages of infection and has minimal association with bursal damage and bursal lymphocyte depletion. Non-B locus-based genetic differences also have a significant impact on survival during early IBDV infection.RESEARCH HIGHLIGHTSThe host B locus and the IBDV pathotype impact development of clinical disease.The host B locus has significant effects on IBDV-induced early mortality.The host B locus has no significant effect on IBDV-induced bursal damage.

Infectious bursal disease (IBD) is an immunosuppressive disease that increases susceptibility to avian coccidiosis, but the contrary is unclear. In a battery trial, this study evaluated whether prior E. tenella (ET) infection of Egyptian Baladi chickens increased the virulence of the very virulent IBD virus. Birds grouped as follows: G1 (control), G2 (ET, 1.5×10⁴ oocysts), G3 (ET, 5×10⁴ oocysts), G4 (IBDV), G5 (G2+BDV), and G6 (G3+IBDV). At 21 days of age (d), chickens were sham- (G1 and 4) or ET- (G2, 3, 5, and 6) challenged. Four days later, G4-6 received IBDV by intranasal/ocular route. The birds were evaluated for growth performance and inspected clinically. The phagocytic test, cloacal viral shedding, and immunological organ index were evaluated on days 28 and 32. On day 28, the bursa of Fabricius (BF), spleen, and caecum were histologically analyzed, and caecal lesions were scored macroscopically. Compared to the G1, all challenged groups displayed worse growth performance (P ≤ 0.01). G5 and 6 outperformed G4 regarding weight gain and FI (P≤0.01), however, they still lagged behind G2 and 3 (P ≤ 0.01). Interestingly, the BF of G2 and 3 had a higher mean severity index (MSI) than G1 (P ≤ 0.01), indicating histological evidence of Eimeria stages. Nonetheless, G4's MSI was higher than G2's and G3's (P ≤ 0.01). Compared to G4, G5 and G6 displayed a substantially lower MSI and a higher BF' index. Mortalities in G4 and G6 were 10% and 5%, respectively. Compared to G4, G5 and 6 displayed increased viral shedding titers (P ≤ 0.01). Regarding coccidiosis, G5 and G6 exhibited lower phagocytic activity and higher oocyst counts and caecal lesion scores than G2 and G3 (P ≤ 0.01), suggesting that exposure to IBDV after ET enhanced ET pathogenicity and reproduction. Conclusions: ET interfered with the IBDV pathogenesis (increase in viral shedding, but less severe lesions compared to mono-infected birds); this could be because prior ET infection modulated T cells.

Research highlights: Metabolomics and 16S rRNA were used to explore the mitigating effect of naringenin on heat stress.Naringenin relieves heat stress through specific metabolic pathways.Changes in gut microbiota caused by naringenin and heat stress may affect host metabolism.

Research highlights: Heterogeneous methods of evaluation are applied in the context of avian disease surveillance, with 26 attributes identified.Sensitivity resulted as the attribute most frequently used, with slight variations in definition across studies.The human behavioural dimension and the effectiveness of spatial coverage in surveillance systems were infrequently addressed.Highlights the need for standardized guidelines for evaluation of disease surveillance.

Research highlights: Velogenic NDV genotype VII.2 detected in vaccinated chickens in southern Vietnam.Isolate was highly virulent with ICPI 1.81 and MDT of 56 h.Rapid onset of disease, severe lesions, and efficient oral/cloacal viral shedding.Findings call for improved NDV surveillance and tailored vaccination in Vietnam.

In the present study, antigen-chitosan-PLGA nanoparticles were explored as the delivery system for inactivated whole infectious bursal disease virus (IBDV) antigens. The immunized birds showed the peak antibody level (ELISA titre 4095.65 ± 55.74) at the 3rd week post-immunization, which was significantly higher than that of the commercial inactivated vaccine (titre 2257 ± 30) (P < 0.0001). The virus-loaded chitosan-coated PLGA nanoparticles induced good cell-mediated immunity. The immunized birds showed better resistance against the challenge infection with a very virulent IBDV. Only one bird out of the five challenged showed viral antigens in the bursa (80% protection), whereas, in the commercial vaccinated group, two chickens showed viral antigens in the bursa (60% protection). The histopathological lesions were also found to be very mild in the same group. The birds which were immunized with the antigen-chitosan-PLGA nanoparticles did not show any sign of immunosuppression. It is concluded that antigen-chitosan-PLGA nanoparticles afford the best protection among the groups, which lays a foundation for further development of a vaccine delivery platform in this line. RESEARCH HIGHLIGHTSFirst report on the use of Chitosan/PLGA nanoparticles with inactivated IBD virus.Nanoparticles prepared by solvent evaporation method.Elicited better humoral and cell-mediated immunity in chickens.Protection is better than commercial vaccine.

Research highlights: North-Western European reassortants (A3B1) were found in Italy for the first time.Local A3B1 clade, related to Russian and Middle Eastern strains, also persisted.Infectious pressure was seemingly stable despite this epidemiological shift.

Avian pseudotuberculosis infection usually presents as well-demarcated visceral necrotic foci, typically affecting the gastrointestinal tract, liver and spleen. This case series describes an atypical presentation of Yersinia pseudotuberculosis (Yptb) characterized by severe chronic myositis, arthritis and osteomyelitis in five village weavers (Ploceus cucullatus), and acute osteomyelitis and myositis associated with septicaemia in an oriental magpie robin (Copsychus saularis) from a zoological collection. Clinical signs of the weavers included lethargy, poor flying ability and focally extensive periarticular and muscular swelling, whereas the magpie robin was found dead without premonitory signs. Radiography revealed focal lytic and proliferative bone lesions with loss of articular congruity and increased radiopacity of skeletal muscles, which was compatible with severe necrotizing, granulomatous osteomyelitis and polyphasic myositis with large intralesional bacterial colonies on histology. Most (n = 4/5) birds with available histology exhibited only mild to moderate heterophilic to histiocytic inflammatory lesions in their intestines, spleen and liver. Bacterial cultures typically yielded Yptb from joint and muscle samples (3/3), and less consistently from visceral organs (6/11) and bone marrow (0/5). Bacterial typing using Fourier-transform infrared (FT-IR) spectroscopy suggested that weaver Yptb strains were closely related. Whole genome sequencing of two Yptb strains identified one as ST14 serotype O:2a and the other ST42 serotype O:1a, with the presence of virulence genes including plasmid-borne yadA and chromosomally encoded virulence genes ail and invA. Weavers may be prone to develop atypical pseudotuberculosis with the musculoskeletal system as a predilection site for bacterial growth and associated granulomatous lesions.

Infectious laryngotracheitis virus (ILTV) remains a significant viral disease in the poultry industry worldwide and vaccination has proven to be an invaluable tool for disease control. Vaccine type, dose and route of administration are important parameters that determine the success of vaccination programmes and control strategies. The current study aimed to investigate the optimal dose for drinking-water vaccination with ΔgG-ILTV, an attenuated glycoprotein G-deficient ILTV vaccine that is efficacious when administered by eye-drop. Three groups of 1-week old specific-pathogen-free chickens were vaccinated with increasing doses of ΔgG-ILTV (10^3.8, 10^4.3 and 10^5.0 plaque-forming units per bird) via the drinking-water. Additional groups of birds included an eye-drop vaccination control (n = 20), and two unvaccinated control groups (n = 20 and 10, respectively). Three weeks after vaccination, all groups, except one unvaccinated control group (n = 10), were challenged with virulent ILTV. Vaccine efficacy was assessed after challenge by recording mortality rate and scoring of clinical signs and gross tracheal pathology. Challenge resulted in severe clinical disease and a high mortality rate in unvaccinated birds. Eye-drop vaccination resulted in complete clinical protection against this specific challenge. The efficacy of drinking-water vaccination showed a direct association with the administered vaccine dose. Results from this study highlight the need for improved understanding of virus-host interactions and immunological responses that occur following drinking-water vaccination, in order to improve the efficacy of vaccination strategies that use this route.